Index: lld/ELF/Config.h
===================================================================
--- lld/ELF/Config.h
+++ lld/ELF/Config.h
@@ -13,6 +13,7 @@
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSet.h"
+#include "llvm/Support/CachePruning.h"
 #include "llvm/Support/CodeGen.h"
 #include "llvm/Support/ELF.h"
 
@@ -161,6 +162,7 @@
   unsigned LTOO;
   unsigned Optimize;
   unsigned ThinLTOJobs;
+  llvm::CachePruningPolicy ThinLTOCachePolicy;
 
   // Returns true if target is 64 bit.
   bool is64Bit() const { return EKind == ELF64LEKind || EKind == ELF64BEKind; }
Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -585,6 +585,9 @@
   Config->Target1Rel = getArg(Args, OPT_target1_rel, OPT_target1_abs, false);
   Config->Target2 = getTarget2(Args);
   Config->ThinLTOCacheDir = getString(Args, OPT_thinlto_cache_dir);
+  Config->ThinLTOCachePolicy =
+      check(parseCachePruningPolicy(getString(Args, OPT_thinlto_cache_policy)),
+            "invalid cache policy");
   Config->ThinLTOJobs = getInteger(Args, OPT_thinlto_jobs, -1u);
   Config->Threads = getArg(Args, OPT_threads, OPT_no_threads, true);
   Config->Trace = Args.hasArg(OPT_trace);
Index: lld/ELF/LTO.cpp
===================================================================
--- lld/ELF/LTO.cpp
+++ lld/ELF/LTO.cpp
@@ -162,6 +162,9 @@
       },
       Cache));
 
+  if (!Config->ThinLTOCacheDir.empty())
+    pruneCache(Config->ThinLTOCacheDir, Config->ThinLTOCachePolicy);
+
   for (unsigned I = 0; I != MaxTasks; ++I) {
     if (Buff[I].empty())
       continue;
Index: lld/ELF/Options.td
===================================================================
--- lld/ELF/Options.td
+++ lld/ELF/Options.td
@@ -394,4 +394,6 @@
 def save_temps: F<"save-temps">;
 def thinlto_cache_dir: J<"thinlto-cache-dir=">,
   HelpText<"Path to ThinLTO cached object file directory">;
+def thinlto_cache_policy: S<"thinlto-cache-policy">,
+  HelpText<"Pruning policy for the ThinLTO cache">;
 def thinlto_jobs: J<"thinlto-jobs=">, HelpText<"Number of ThinLTO jobs">;
Index: lld/test/ELF/lto/cache.ll
===================================================================
--- lld/test/ELF/lto/cache.ll
+++ lld/test/ELF/lto/cache.ll
@@ -3,10 +3,13 @@
 ; RUN: opt -module-hash -module-summary %s -o %t.o
 ; RUN: opt -module-hash -module-summary %p/Inputs/cache.ll -o %t2.o
 
-; RUN: rm -Rf %t.cache
-; RUN: ld.lld --thinlto-cache-dir=%t.cache -o %t3 %t2.o %t.o
+; RUN: rm -Rf %t.cache && mkdir %t.cache
+; Create a file that will be removed by cache pruning due to age.
+; RUN: touch -d 1970-01-01 %t.cache/foo
+; RUN: ld.lld --thinlto-cache-dir=%t.cache --thinlto-cache-policy prune_after=1h -o %t3 %t2.o %t.o
 
-; RUN: ls %t.cache | count 2
+; Two cached objects, plus a timestamp file, minus the file we removed.
+; RUN: ls %t.cache | count 3
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"